Reversing switch actuator for fluid motor

ABSTRACT

A fluid motor having piston actuated switches on the cylinder heads thereof which control operation of a solenoid reversing valve to achieve automatic reciprocation of the piston. Each switch actuator comprises a radially positioned assembly which includes a relatively large diameter ball which is engaged by the piston as it approaches the end of its stroke, a large diameter spring follower which is spring biased against the ball, and a small diameter actuator rod which has sliding sealed engagement with a switch retainer in the cylinder head, the radially inner end portion of the rod being engaged with the spring follower and the radially outer end portion of the rod being engageable with the switch plunger to close the switch contacts to reverse the piston when the ball, follower, and rod have been moved radially outwardly by the engagement of the piston with the ball.

1451 May 9, 1972 22 Filed:

[54] REVERSING SWITCH ACTUATOR FO FLUID MOTOR [72] Inventor: Beldon L.Rich, Buffalo Grove, Ill.

[73] Assignee: Parker-Hannifin Corporation, Cleveland,

Ohio

Dec. 4, 1970 [2]] AppI.No.: 95,311

FOREIGN PATENTS OR APPLICATIONS 628,873 9/1949 Great Britain .9l/ 275Primary Examiner-Paul E. Maslousky Attorney-Oberlin, Maky, Donnelly &Renner [5 7] ABSTRACT A fluid motor having piston actuated switches onthe cylinder heads thereof which control operation of a solenoidreversing valve to achieve automatic reciprocation of the piston. Eachswitch actuator comprises a radially positioned assembly which includesa relatively large diameter ball which is engaged by the piston as itapproaches the end of its stroke, a large diameter spring follower whichis spring biased against the ball, and a small diameter actuator rodwhich has sliding sealed engagement with a switch retainer in thecylinder head, the radially inner end portion of the rod being engagedwith the spring follower and the radially outer end portion of the rodbeing engageable with the switch plunger to close the switch contacts toreverse the piston when theball, follower, and rod have been movedradially outwardly by the engagement of the piston with the ball.

12 Claims, 3 Drawing Figures 1 lul .PATENTEDm 9I972 INVENTOR. I

BEL DON L. RICH BY I Il hll F ATTORNEYS REVERSING SWITCHACTUATOR F ORFLUID MOTOR I BACKGROUND OF THE INVENTION It is known to provide aradially movable switch actuating rod' engaged by a piston as the latterapproaches the end of its stroke but because of the side load or bendingload on the rod exerted by axial movement of the piston into engagementwith loads when the rod is being moved radially outwardly by the piston,the rod then being exposed to low pressure on the return side of themotor.

SUMMARY OF THE INVENTION It is a principal object of this invention toprovide a simple and efficient form of'switch actuator for a fluid motorin which a relatively large diameter ball is engaged by the piston, theball being engaged with the plane face of a spring follower whichtransmits the ball motion to a small diameter switch actuating rod.Because the ball engages a plane face of the large diameter followerthere is no alignment problem of the ball guide bore with the actuatorrod guide bore. Another characterizing feature of this invention is thatas the ball is engaged by the piston it tends to be moved axially butthere is, in addition, a tendency to rotate the ball so as not to imposean axial or side load on the radially movable spring follower and switchactuator rod.

Other objects and advantages of the present invention will becomeapparent as'the following-description proceeds.

BRIEF DESCRIPTIONOF THE DRAWING DETAILED DESCRIPTION OF THE INVENTION InFIG. 1 is shown a schematic piping and wiring diagram of the left theright-hand switch 5 will be opened but the reversing valve 4 will remainin the actuated position and as the piston 8 approaches the end of itsleft-hand stroke, the left-hand switch 5 will be closed to energize theleft-hand solenoid 9 so as to shift the valve 4 to the position shown inFIG. 1 thereby to conduct fluid under pressure again into the rod end 6with the displaced fluid being conducted to the reservoir 2 via valve 4.7

Because both switches 5 and actuating mechanisms therefor are ofsubstantially identical construction, except for the diameters of thecam rod 11 and cam sleeve 12 on opposite sides of the piston 8, only oneof the switches 5 and switch actuating mechanisms have been illustratedin FIGS. 2 and 3. As shown in FIG. 2, the cylinder head 7 is providedwith'an axial bore 14 into which the piston cam rod 11 loosely extendsas e the piston 8 moves to the right. The cylinder head 7 also has a afluid motor control system for effecting automatic reversal.

of a double acting fluid motor 1 of the piston-cylinder type. Thereference numeral 2 denotes a fluid reservoir from which the pump 3draws fluid for supplying fluid under pressure into either the rod endor the head end of the motor 1 via a solenoid operated reversing 'valve4. Switches 5;5 are mounted on the respective cylinder heads 6 and 7 andare adapted to be closed by the movement of the piston 8 toward therespective heads 6 and 7 to energize the respective solenoids 9 and 10for effecting operation of the reversing valve 4 so as to cause movementof the piston 8 in the opposite direction.

For example, when the piston 8 is moving to the right, the reversingvalve 4 is in the position shown whereby fluid under pressure isconducted into the rod end 6 of the cylinder 1 and the fluid displacedfrom the head end 7 of the cylinder is conducted through the reversingvalve. 4 into the reservoir 2. As the piston 8 approaches the righthandend of its stroke, the right-hand switch 5 is closed to energize theright-hand solenoid 10 whereby the valve 4 is shifted so that fluidunder pressure is now conducted into the head end 7 of the cylinderwhile the fluid displaced from the rod end 6 is conducted through thevalve 4 to the reservoir 2. As the piston 8 moves to radial bore 15 inwhich is seated a ball guide ring 16 which has a ball seat 17 whichdetermines the radially innermost position of the ball 18 as shown inFIG. 3 so as to be in the path of movement of the piston cam rod 11.

Screwed into the radial bore 15 is a switch retainer 19 which is sealedin the bore as by means of the packing ring 20, and which has a threadedupper end extending through an opening in the switch box 21, the lattercontaining the limit switch 5 having its switch plunger 23 disposed formovement coaxially with the axis of the retainer 19. The switch box 21is securely mounted on the cylinder head 7 as by means of the lock nut24 which is threaded onto the upper end portion of the retainer 19.

Compressed between the switch retainer 19 and a spring follower 25 whichhas a plane radially inner face engaged with the radially outermostportion of the ball 18 is a spring 26 which yieldably holds the ball 18in its seat 17 so that the radially inner portion of the ball 18 isdisposed for engagement by the piston cam rod 11.

The radial movement of the ball 18 and follower 25 istransmitted to theswitch plunger 23 for closing the contacts (not shown) in switch 5through a small diameter actuating rod 27 which may be press fitted orotherwise secured to the spring follower 25 and which has a closesliding fit in a central bore in the switch retainer 19. The actuatorrod 27 is slidably sealed in the bore in retainer 19 as by means of anO-ring 28.

As an example, in a 3,000 psi. cylinder 1 in which 1/16- inch radialmovement of the ball 18, follower 25, and actuator rod 27 is, desired, a3/8-inch diameter ball 18 has been found satisfactory with an actuatingrod 27 of about l/l6-inch diameter. Thus, the spring 26 needs only exertabout a 10 pound radial inward force to prevent radial outward movementof the actuator rod 27 under the influence of 3,000 psi. pressure.

The ball seat 17 is as shown provided with a leakage slot 29 so that theball 18 and follower 25 will be pressure balanced so that only theeffective, area of the small actuating rod 27 is acted upon by the highpressure. The upper end of the actuating rod 27 may be provided with aplastic or like switch engaging button 30.

As shown in FIG. 3, as the piston cam rod 11 moves to the right near theend of the stroke of the piston 8, it initially contacts the ball 18 at31 to apply axial and radial forces thereon which will tend to shift theball 18 toward the right and upward away from the seat 17 as themovement of the piston cam rod 11 continues. However, such forces alsotend to cause rotation of the ball 18 in the direction of the arrow thusto tend to negate the side load transmitted to the follower 25 andslender rod 27.

Another feature of the present invention is that because the ball 18 hascontact with a plane face of the follower 25, the ball guide bore inring 16 and the actuator rod guide bore in retainer 19 need not beperfectly concentric. In other words, any eccentricity of these guidebores does not cause any binding action which would interfere withmovement of the ball 18 or rod 27 in their respective guide bores.

1, therefore, particularly point out and distinctly claim as myinvention:

. larged portion also longitudinally movable in said housing, and

spring means in said housing biasing said radially enlarged portionagainst said ball to position the latter in the path of movement of cammeans on said component; said cam means, upon movement of said componentto a predetermined position, being operative by engagement with saidball to longitudinally move said rod to switch actuating position; andmeans responsive to actuation of said switch to initiate movement ofsaid component in a direction away from such predetermined position. v

2. The switch assembly of claim 1 wherein said ball and said enlargedportion are exposed to fluid pressure but are pressure balanced; saidrod being longitudinally slidably sealed in said housing and being ofrelatively small diameter as compared with the diameter of said ball andof said radially enlarged portion whereby said spring means needs onlyto overcome a relatively small force imposed on said rod by fluidpressure acting on the small effective area thereof.

3. The switch assembly of claim 1 wherein said radially enlarged portionhas a plane end face engaged with said ball thus to accommodateeccentricity of said rod and ball without binding of said rod in saidhousing.

4. The switch assembly of claim 1 wherein a duplicate switch assembly isdisposed at the other end of said motor and wherein said component hasanother cam means for engaging and moving the ball of said duplicateswitch assembly for actuation of the switch thereof to initiate movementof said component in a direction away from an opposite predeterminedposition whereby said component is automatically reciprocated betweensuch predetermined positions.

5. The switch assembly of claim 1 wherein the path of movement of saidcomponent is angularly related to the path of movement of said ball androd, said ball having lateral sliding engagement with said radiallyenlarged portion thus to substantially eliminate transfer of side loadfrom said ball to said rod.

6. The switch assembly of claim 5 wherein movement of said ball byengagement of said cam means therewith tends to rotate said ball in adirection to further decrease tendency of transmission of side load tosaid rod.

7. The switch assembly of claim 1 wherein said last-named meanscomprises a solenoid operated valve which, upon actuation of saidswitch, conducts fluid pressure into said motor to move said componentaway from such predetermined position. a

8. A switch assembly for the cylinder head of a fluid motor of the typehaving a piston movable by fluid pressure in the cylinder thereof towardand away from said cylinder head; said assembly comprising cam means onsaid piston movable into and out of a central axial bore in saidcylinder head; said cylinder head having a radial bore intersecting saidcentral bore; a switch secured .to said cylinder head; switch actuatingmeans in said radial bore including a switch actuating rod coaxial withsaid radialbore having a radially outer end portion engageable with saidswitch to actuate the latter and having a laterally enlarged radiallyinner end portion, a ball adjacent said enlarged portion, said springmeans biasing said enlarged portion against said ball to position thelatter with a radially inner portion thereof disposed in the path ofmovement of said cam means; said cam means being operative by engagementwith said ball to radially outwardly move said ball and said rod thus toactuate said switch; and means responsive to actuation of said switch todirect fluid under pressure into said cylinder head to initiate movementof said piston away from said cylinder head.

9. The switch assembly of claim 8 wherein said ball and said enlargedportion are exposed to fluid pressure in said cylinder head but arepressure balanced; said rod being radially slidably sealed in saidcylinder head and being of relatively small diameter as compared withthe diameter of said ball and of said enlarged portion whereby saidspring means needs only to overcome a relatively small force imposed onsaid rod by fluid pressure acting on the small effective area thereof.

10. The switch assembly of claim 8 wherein a switch retainer is securedin the radially outer portion of said radial bore to provide means bywhich said switch is secured to said cylinder head and to provide aguide bore for radial movement of said rod.

11. The switch assembly of claim 10 wherein said radial bore adjacentits radially inner portion provides a guide bore for radial movement ofsaid ball and a seat to determine the radially innermost position ofsaid ball so as to be engaged by said cam means.

12. The switch assembly of claim 11 wherein said enlarged portion has aplane end face engaged with said ball thus to accommodate eccentricityof said ball and rod guide bores without binding of said rod in saidretainer.

1. A switch assembly for a fluid motor of the type having a componentmovable therein by fluid pressure, said assembly comprising a housingsecured to said motor at one end thereof; a switch on said housing;switch actuating means in said housing including a switch actuating rodlongitudinally movable in said housing and having one end portionengageable with said switch to actuate the latter and having a radiallyenlarged opposite end portion, a ball adjacent said radially enlargedportion also longitudinally movable in said housing, and spring means insaid housing biasing said radially enlarged portion against said ball toposition the latter in the path of movement of cam means on saidcomponent; said cam means, upon movement of said component to apredetermined position, being operative by engagement with said ball tolongitudinally move said rod to switch actuating position; and meansresponsive to actuation of said switch to initiate movement of saidcomponent in a direction away from such predetermined position.
 2. Theswitch assembly of claim 1 wherein said ball and said enlarged portionare exposed to fluid pressure but are pressure balanced; said rod beinglongitudinally slidably sealed in said housing and being of relativelysmall diameter as compared with the diameter of said ball and of saidradially enlarged portion whereby said spring means needs only toovercome a relatively small force imposed on said rod by fluid pressureacting on the small effective area thereof.
 3. The switch assembly ofclaim 1 wherein said radially enlarged portion has a plane end faceengaged with said ball thus to accommodate eccentricity of said rod andball without binding of said rod in said housing.
 4. The switch assemblyof claim 1 wherein a duplicate switch assembly is disposed at the otherend of said motor and wherein said component has another cam means forengaging and moving the ball of said duplicate switch assembly foractuation of the switch thereof to initiate movement of said componentin a direction away from an opposite predetermined position whereby saidcomponent is automatically reciprocated between such predeterminedpositions.
 5. The switch assembly of claim 1 wherein the path ofmovement of said component is angularly related to the path of movementof said ball and rod, said ball having lateral sliding engagement withsaid radially enlarged portion thus to substantially eliminate transferof side load from said ball to said rod.
 6. The switch assembly of claim5 wherein movement of said ball by engagement Of said cam meanstherewith tends to rotate said ball in a direction to further decreasetendency of transmission of side load to said rod.
 7. The switchassembly of claim 1 wherein said last-named means comprises a solenoidoperated valve which, upon actuation of said switch, conducts fluidpressure into said motor to move said component away from suchpredetermined position.
 8. A switch assembly for the cylinder head of afluid motor of the type having a piston movable by fluid pressure in thecylinder thereof toward and away from said cylinder head; said assemblycomprising cam means on said piston movable into and out of a centralaxial bore in said cylinder head; said cylinder head having a radialbore intersecting said central bore; a switch secured to said cylinderhead; switch actuating means in said radial bore including a switchactuating rod coaxial with said radial bore having a radially outer endportion engageable with said switch to actuate the latter and having alaterally enlarged radially inner end portion, a ball adjacent saidenlarged portion, said spring means biasing said enlarged portionagainst said ball to position the latter with a radially inner portionthereof disposed in the path of movement of said cam means; said cammeans being operative by engagement with said ball to radially outwardlymove said ball and said rod thus to actuate said switch; and meansresponsive to actuation of said switch to direct fluid under pressureinto said cylinder head to initiate movement of said piston away fromsaid cylinder head.
 9. The switch assembly of claim 8 wherein said balland said enlarged portion are exposed to fluid pressure in said cylinderhead but are pressure balanced; said rod being radially slidably sealedin said cylinder head and being of relatively small diameter as comparedwith the diameter of said ball and of said enlarged portion whereby saidspring means needs only to overcome a relatively small force imposed onsaid rod by fluid pressure acting on the small effective area thereof.10. The switch assembly of claim 8 wherein a switch retainer is securedin the radially outer portion of said radial bore to provide means bywhich said switch is secured to said cylinder head and to provide aguide bore for radial movement of said rod.
 11. The switch assembly ofclaim 10 wherein said radial bore adjacent its radially inner portionprovides a guide bore for radial movement of said ball and a seat todetermine the radially innermost position of said ball so as to beengaged by said cam means.
 12. The switch assembly of claim 11 whereinsaid enlarged portion has a plane end face engaged with said ball thusto accommodate eccentricity of said ball and rod guide bores withoutbinding of said rod in said retainer.